1. Field of the Invention
The present invention relates to a toroidal-type continuously variable transmission and a continuously variable transmission apparatus for use in a power transmission system of a vehicle.
2. Description of the Related Art
Conventionally, in a power transmission system of a vehicle, there is used a toroidal-type continuously variable transmission of a double cavity type. The toroidal-type continuously variable transmission of a double cavity type, for example, as disclosed in JP-A-2000-9196 or in Japanese Patent No. 2629786, includes a pair of input disks, a pair of output disks, a plurality of power rollers, a pressing device and an output gear. The pair of input disks"" are disposed in such a manner as to be spaced from each other in the axial direction of an input shaft. The pair of output disks are interposed between the two input disks and opposed to their associated input disks. The plurality of power rollers are interposed between the mutually opposed input and output disks. The pressing device presses the input disk toward the output disk. The output gear rotates integrally with the output disks.
Further, there has been developed a continuously variable transmission apparatus which is a combination of a toroidal-type continuously variable transmission using a loading cam with a planetary gear mechanism. For example, there is known a continuously variable transmission apparatus, in which a toroidal-type continuously variable transmission and a planetary gear mechanism are disposed substantially concentrically with an engine shaft, and power is circulated between the input shaft and the output gear of the toroidal-type continuously variable transmission. And, the planetary gear mechanism includes a clutch capable of switching a low speed mode, a high speed mod, and a retreating mode over one another. In this type of continuously variable transmission apparatus, for example, as shown in DE19821417A1, in order to prevent a pressing force by the loading cam from increasing excessively, a hollow shaft is disposed on the outer periphery side of the input shaft in such a manner as to be concentric with the input shaft, and first and second input disks are connected to each other by the hollow shaft, whereby torque transmitted from the input shaft can be distributed to the pair of input disks.
In a toroidal-type continuously variable transmission, it is important to supply a sufficient quantity of lubricating oil to the portions of the toroidal-type continuously variable transmission to be lubricated, for example, bearings and ball splines. For example, as disclosed in JP-A-2000-9196, in order to lubricate bearings or ball splines for supporting disks or gears, an oil passage is formed in the interior of an input shaft, and a hole which communicates with the oil passage is opened up in the vicinity of the bearings or ball splines.
However, the above described toroidal-type continuously variable transmission structured such that the input shaft penetrates through the hollow shaft restricts the outside diameter of the penetrating portion of the input shaft, where the input shaft penetrates through the hollow shaft. Therefore, there arises a problem that, when an oil hole is formed in the input shaft, there occurs an excessive stress in the periphery of the oil hole. In order to lower the level of the stress, it is effective to increase the sizes of the parts of the toroidal-type continuously variable transmission. However, this raises another problem that the whole size of the toroidal-type continuously variable transmission is increased and thus the weight thereof is also increased.
Especially, a tensile load from the loading cam and a torsional load due to the engine torque are applied to the input shaft at the same time. Also, since stresses concentrate in the vicinity of the oil hole, there is generated an excessive stress. In particular, in the portion where the input shaft penetrates through the hollow shaft, the outside diameter of the input shaft is limited according to the inside diameter of the hollow shaft and thus the shaft diameter thereof is reduced, thereby raising the level of the stress. This makes it more difficult to form an oil hole in the input shaft. Even in case where the hardness of the periphery of the oil hole was increased by heat treatment, the strength of the oil hole could not be increased so much due to the existence of an abnormal layer caused by heat treatment
By the way, as disclosed in Japanese Patent No. 2629786, there is proposed a structure that a clearance between the input shaft and hollow shaft is used as a lubricating oil passage. However, in this structure, of the whole length of the input shaft, the oil hole is formed in the portion (the portion where the shaft diameter is small) of the input shaft that penetrates through the hollow shaft; and, therefore, there is a possibility that the input shaft can be damaged by the excessive stress concentration.
The present invention aims at eliminating the above drawbacks found in the conventional toroidal-type continuously variable transmissions. Accordingly, it is an object of the invention to provide a toroidal-type continuously variable transmission which can provide excellent lubricating performance without lowering the strength of the input shaft.
To attain the above object, according to the present invention, there is provided a toroidal-type continuously variable transmission, including: an input shaft transmitting power from an engine; a pair of input disks disposed in such a manner as to be spaced apart from each other in an axial direction of the input shaft; a pair of output disks interposed between the pair of input disks in such a manner as to be opposed to the respective input disks; a pressing mechanism pressing the input disk toward the output disk; and, a hollow shaft disposed around an outer periphery of the input shaft concentrically with the input shaft, and connecting the pair of input disks to each other. The input shaft defines an oil hole formed in a no-penetrating portion of the input shaft where the input shaft does not penetrate through the hollow shaft, and opened on an outer peripheral surface of the no-penetrating portion. An oil passage is formed between an inner peripheral surface of the hollow shaft and an outer peripheral surface of a penetrating portion of the input shaft where the input shaft penetrates through the hollow shaft.
Further, according to the present invention, there is provided a continuously variable transmission apparatus including a combination of a toroidal-type continuously variable transmission with a planetary gear mechanism, the toroidal-type continuously variable transmission having: an input shaft transmitting power from an engine; a pair of input disks disposed in such a manner as to be spaced apart from each other in an axial direction of the input shaft; a pair of output disks interposed between the pair of input disks in such a manner as to be opposed to the respective input disks; a pressing mechanism pressing the input disk toward the output disk; and, a hollow shaft disposed around an outer periphery of the input shaft concentrically with the input shaft, and connecting the pair of input disks to each other. The input shaft defines an oil hole formed in a no-penetrating portion of the input shaft where the input shaft does not penetrate through the hollow shaft, and opened on an outer peripheral surface of the no-penetrating portion. An oil passage is formed between an inner peripheral surface of the hollow shaft and an outer peripheral surface of a penetrating portion of the input shaft where the input shaft penetrates through the hollow shaft. And, the planetary gear mechanism has: a first rotary body rotatable by the input shaft; a second rotary body rotatable by the output disk; and, a clutch switching over the rotation movements of the first and second rotary bodies to any of an advancing side high speed mode, an advancing side low speed mode and a retreating mode to transmit the same to the output shaft.
Moreover, according to the present invention, there is also provided a continuously variable transmission apparatus including a combination of a toroidal-type continuously variable transmission with a planetary gear mechanism, the toroidal-type continuously variable transmission having: an input shaft transmitting power from an engine; an output shaft disposed in parallel to the input shaft; a pair of input disks disposed in such a manner as to be spaced apart from each other in an axial direction of the input shaft; a pair of output disks interposed between the pair of input disks in such a manner as to be opposed to the respective input disks; a pressing mechanism pressing the input disk toward the output disk; and, a hollow shaft disposed around an outer periphery of the input shaft concentrically with the input shaft, and connecting the pair of input disks to each other. The input shaft defines an oil hole formed in a no-penetrating portion of the input shaft where the input shaft does not penetrate through the hollow shaft, and opened on an outer peripheral surface of the no-penetrating portion. An oil passage is formed between an inner peripheral surface of the hollow shaft and an outer peripheral surface of a penetrating portion of the input shaft where the input shaft penetrates through the hollow shaft. And, the planetary gear mechanism has: a linking member rotatable integrally with the input shaft; a first rotary body rotatable integrally with the linking member; a second rotary body rotatable by the output disk; and, a clutch for switching over the rotation movements of the first and second rotary bodies to any of an advancing side high speed mode, an advancing side low speed mode and a retreating mode to transmit the same to the output shaft.
According to the invention, in the input shaft to which a tensile load and a torsional load are applied, no oil hole is formed in the penetrating portion thereof where the input shaft penetrates through the hollow shaft but an oil hole is formed in the no-penetrating portion thereof where the input shaft does penetrate through the hollow shaft. Therefore, a stress in the periphery of the oil hole can be reduced. Also, since the shaft diameter of the oil hole forming portion (that is, the portion of the input shaft where the input shaft does not penetrate through the hollow shaft) can be set larger than that of the portion of the input shaft where the input shaft penetrates through the hollow shaft, even in case where the oil hole is formed in the oil hole forming portion of the input shaft, there can be eliminated a fear that there can occur excessive stress concentration. On the other hand, in the case of the hollow shaft, a tensile load is hardly applied to the hollow shaft but the hollow shaft is simply required to transmit torque therethrough; and, the torque to be transmitted through the hollow shaft is at most about half of the engine torque. Therefore, even in case where an oil flow hole is formed in the hollow shaft, there is no possibility that an excessive stress can be generated.
According to the invention, a groove may be formed in the outer peripheral surface of the input shaft to thereby facilitate the flow of the lubricating oil. This groove may be a linear-shaped groove extending along the axial direction of the input shaft, or a spiral-shaped groove, or may be composed of a plurality of grooves.
Preferably, there may be employed a spiral groove drawing a spiral which, in consideration of the direction of the torsion moment applied to the input shaft, extends in the opposite direction to the rotation direction of the input shaft from the torque inputting side end portion of the input shaft toward the torque transmitting side end portion of the input shaft. That is, by forming the spiral groove in the direction where the tensile stress acts, the strength of the input shaft can be further enhanced.
By the way, the invention can also be applied to such a continuously variable transmission apparatus as disclosed in Japanese Patent No. 2629786, in which the torque transmitted from the engine shaft is transmitted only to a toroidal-type continuously variable transmission. Also, the invention can also be applied to a continuously variable transmission apparatus of a so called geared neutral type which is constructed by a combination of a toroidal-type continuously variable transmission and a planetary gear mechanism.